The present invention relates to a semiconductor laser module to be optically coupled to the optical fiber, particularly to, a semiconductor laser module to be optically coupled to the optical fiber provided to the branch line, subscriber line, and the like.
In recent years, even in the branch line system, subscriber line system and the like (hereinafter, referred to simply as “subscriber line system”), a Single Mode Fiber (hereinafter, referred to simply as “SMF”) has been used and spread from the point of view of the high speed data transmission. Usually, for such as upload from a communication apparatus in home, a semiconductor laser is used as a light source and positioned so as to efficiently couple to the optical fiber.
FIG. 7 is a cross-sectional view illustrating an exemplary configuration of a conventional semiconductor laser module using a micro lens (refer, for example, to the patent document 1). In FIG. 7, a semiconductor laser 71 is arranged such that it is mounted on a heat sink 72 inside a package consisting of a stem 73 and cap 74 and optically couples to a SMF in a ferrule 78 via a micro lens 75 and spherical lens 76 held inside the sleeve 77. Hereat, a transmitted light from the semiconductor laser 71 is transformed to a parallel beam by the micro lens 75 working as a collimator, and then collected to the core in the cross section of the SMF by the spherical lens 76 working as a collective lens to couple to the SMF, and thereby propagating inside the SMF.
This semiconductor laser module is assembled as follows. First, the semiconductor laser 71 and micro lens 75 are positioned, and then the cap 74 is solidly attached to the stem 73 thereby ceiling the semiconductor laser 71. Next, the optical fiber ferrule 78 is inserted into the sleeve 77, in which the spherical lens 76 is aligned inside, next, the sleeve 77 is put on the cap 74, and then adjustment of positioning is performed between the sleeve 77 and the cap 74 with respect to the x axis and y axis. Finally, an adjustment of positioning is performed between the spherical lens 76 and the ferrule 78 with respect to the z axis, and then, at the position where optical coupling is optimal, the welding portions 79a, 79b are fixed by spot-welding technique using YAG laser.
FIG. 8 is a cross-sectional view illustrating an exemplary configuration of the semiconductor laser module of conventional butterfly-type (refer, for example, to the patent document 2). In FIG. 8, a semiconductor laser 81 is arranged such that it is aligned on a heat sink 82a mounted inside the package consisting of a stem 83 and cap 84 and optically couples to a SMF 88 held by an optical fiber holder 87 via a collective lens 85 held inside the package by a lens holder 86a and supporting stick 86b. Here, the heat sink 82a is aligned to connect with an electronic cooling device 82c such as a Peltier device via a substrate 82b with a high thermal conductivity so as to have low thermal resistance. Further, arrangements for securing the optical coupling are carried out between the semiconductor laser 81 and the collective lens 85 and also between the collective lens 85 and the optical fiber holder 87, with respect to the 3 directions: the x-, y-, and z-axes.
[Patent document 1] Japanese Patent Application Laid-Open Publication No. 05-121841
[Patent document 2] Japanese Patent Application Laid-Open Publication No. 09-251120
However, the conventional semiconductor laser module has a problem that severe arrangement burdens are required to perform the 2- or 3-dimensional positioning among the semiconductor laser, SMF, and the lens system aligned therebetween, in order to keep the optical coupling between the semiconductor laser and SMF high. Owing to these arrangement burdens required for the positioning, it is difficult to realize a compact arrangement, a low price, etc suitable for market use.
Considering the aforementioned present situation, the object of the present invention is to provide a semiconductor laser module capable of reducing the arrangement burdens required to the positioning of the optical system than the conventional one.